This invention relates generally to fuel cells, and more particularly to methods of fuel cell system start-up under frozen conditions with ice blocking an anode cell.
Starting a fuel cell system for automotive applications involves a balance between reliability, durability, and time until acceptable drive away (start length). Reliability involves ensuring that sufficient reactant is present across the whole active area on both sides of the membrane so that full current can be supported. This must be done without exceeding the hydrogen emission requirements. Factors such as hardware layout, hardware reliability, or various ambient conditions, such as temperature, pressure, and humidity, also impact the strategy used to start a fuel cell system successfully.
Under freeze start conditions, sometimes a cell is or becomes blocked with ice. If the anode is blocked, after consuming all of the hydrogen within the cell, the cell goes to negative voltages, even at low power. Another indication of a cell blockage is that even after the load is removed, it takes a long time to get back to the open circuit voltage (OCV), so the interpretation is that diffusion (or a very slow leak) is needed to get hydrogen back into the cell.
Therefore, there is a need for a reliable start-up method under freeze conditions.